Adjustable seating system

ABSTRACT

A wheelchair includes a seat back and a frame rail. The seat back can be moved relative to the frame rail between a folded position and an unfolded and locked position. A first releasable locking mechanism releasably locks the seat back in the unfolded and locked position. A second releasable locking mechanism releasably locks the seat back at any selected one of a plurality of different angles relative to the frame rail. The seat back can be folded and unfolded without adjusting the seat back angle. The seat back has a portion that slides along the frame rail as the seat back angle is adjusted. The length of the seat back varies as the seat back angle is adjusted. The seat back includes a back cane that is pivotally connected with the frame rail by a pivot bracket. The back cane is fixedly connected to the pivot bracket. The pivot bracket pivots relative to the frame rail when the seat back is moved from the unfolded position to the folded position.

RELATED APPLICATION

This application claims the benefit of U.S. Provisional Application No.60/364,301 filed Mar. 13, 2002.

FIELD OF THE INVENTION

The present invention is directed to wheelchairs and, more particularly,to seating systems for wheelchairs.

BACKGROUND OF THE INVENTION

Adjustable seating systems are important features of wheelchairs. Theadjustability of such seating systems allows a user of the wheelchair toadjust various aspects of the seating system in order to provide themost comfortable seating arrangement. However, prior art adjustableseating systems suffer from several disadvantages. For example, someadjustable seating systems require the use of tools and detailedinstructions typically only found in the wheelchair owner's manual toaffect a seat adjustment. Such systems are often confusing andnon-intuitive to the wheelchair user. Other adjustable seating systemsdo not provide independent adjustability. For example, some adjustableseating systems provide a folding seat back mechanism that, when used,changes or resets other adjustable seating system features such as theseat-back angle adjustment.

U.S. Pat. No. 6,311,999 discloses a wheelchair seat in which the angleof the seat back is adjustable relative to the seat bottom cushion, andthe seat back can be folded down flat (forward) onto the seat bottomcushion, while retaining the seat back adjustment angle.

SUMMARY OF THE INVENTION

The present invention relates to a wheelchair that includes a seat backand a frame rail. The seat back can be moved relative to the frame railbetween a folded position and an unfolded and locked position. A firstreleasable locking mechanism releasably locks the seat back in theunfolded and locked position. A second releasable locking mechanismreleasably locks the seat back at any selected one of a plurality ofdifferent angles relative to the frame rail. The seat back can be foldedand unfolded without adjusting the seat back angle.

The seat back has a portion that slides along the frame rail as the seatback angle is adjusted. The length of the seat back varies as the seatback angle is adjusted. The seat back includes a back cane that ispivotally connected with the frame rail by a pivot bracket. The backcane is fixedly connected to the pivot bracket. The pivot bracket pivotsrelative to the frame rail when the seat back is moved from the unfoldedposition to the folded position.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other features of the present invention will becomeapparent to one skilled in the art to which the present inventionrelates upon consideration of the following description of the inventionwith reference to the accompanying drawings, in which:

FIG. 1 is a perspective view of a portion of a wheelchair frameincluding a seat back adjustment mechanism in accordance with thepresent invention;

FIG. 2A is an exploded perspective view of the seat back adjustmentmechanism;

FIG. 2B is an exploded perspective view of selected parts of the seatback adjustment mechanism;

FIG. 3 is a side elevational view of the seat back adjustment mechanism,shown in a first position;

FIG. 4 is a rear elevational view of the seat back adjustment mechanism,shown in a first position;

FIG. 5 is a view similar to FIG. 4 showing the seat back adjustmentmechanism in a second or folded position;

FIG. 6 is a side elevational view of the seat back adjustment mechanism,shown in the second or folded position;

FIGS. 7–9 are a series side elevational views showing the seat backadjustment mechanism supporting the seat back in different angularorientations;

FIG. 10 is a sectional view of a portion of the seat back adjustmentmechanism; and

FIG. 11 is another sectional view of a portion of the seat backadjustment mechanism, taken along line 11—11 of FIG. 10.

DETAILED DESCRIPTION

FIG. 1 is a perspective view of a wheelchair 100 incorporating oneembodiment of a seat back fold-down and adjustable seat back anglemechanism in accordance with the present invention. Wheelchair 100 has aframe 102 that includes a first side frame 104 and a second side frame106. Side frames 104 and 106 are mirror constructions of each other and,therefore, only side frame 104 will be discussed in particular with theunderstanding that the discussion equally applies to side frame 106.

Side frame 104 has frame portions 108, 110, and 112 collectively forminga lower side frame portion. Side frame 104 further has a frame portion114 that is pivotally connected to frame portion 112 via pivotalconnection 116. Frame portion 114 forms an upper side frame portion.Pivotal connection 116 has a pivot lug assembly that includes a pivotlug fork, pivot lug, and a pivot pin for inserting through the pivot lugfork and pivot lug. For example, one such suitable pivot lug assembly indescribed in U.S. Pat. No. 5,267,745 to Robertson et al., which ishereby fully incorporated by reference. Preferably, the pivot lug forkis rigidly attached to frame portion 112 and the pivot lug is rigidlyattached to a first end of frame portion 114. Frame portion 114 furtherhas a second end that includes fork member 118. Fork member 118 isconfigured to accept a seat-angle adjust plate 120 between its forkmembers. Seat-angle adjust plate 120 is rigidly affixed to frame portion110 and includes a plurality of vertically spaced-apart mounting holesthat are used to secure fork member 118 with a nut and bolt fastener.Configured as such, the angle of frame portion 114 can be adjusted bypivoting frame portion 114 about pivotal connection 116 and securingsuch angle by appropriately fastening fork member 118 to seat-angleadjust plate 120.

A clamp 122 is provided on frame portion 108 for attaching an axle tubethereto resulting in the axle tube being connected between side frames104 and 106 by a similar clamp on side frame 106. One such suitableclamp and axle tube assembly is described in U.S. Pat. No. 5,851,018 toCurran et al., which is hereby fully incorporated by reference. The axletube is used to secure the left and right-side drive wheels towheelchair 100 for propulsion. The axle tube also provides additionalrigidity to frame 102 between side frames 104 and 106. In this regard, afootrest 109 is also provided that interfaces with frame portion 112 andits equivalent in side frame 106 to provide further rigidity towheelchair 100.

Wheelchair 100 further includes a seat back fold-down mechanism and anadjustable seat back angle mechanism, collectively shown as 124. Sideframe 106 includes a similar seat back fold-down and adjustable seatback angle mechanism, collectively shown as 136, which is of mirrorconstruction to seat back fold-down and adjustable seat back anglemechanism 124. In this regard, a seat back assembly 135 is provided thatincludes a seat back cushion (not shown) that is preferably removablyaffixed to a set of back canes 130 and 134. The seat back fold-down andadjustable seat back angle mechanisms 124 and 136 connect the back canes130 and 134 to frame 102 via frame portion 114 and its equivalent inside frame 106. A handle bar 132 is provided between back canes 130 and134 to provide rigidity between the back canes 130 and 134 and to enablefolding the seat back toward the frame portion 114 or unfolding the seatback away from frame portion 114.

FIG. 2A shows an exploded view of the seat back 135 fold-down andadjustable seat back angle mechanism 124. FIG. 2B is a reverse-angleexploded perspective of FIG. 2A that further illustrates the features ofthe present embodiment. In FIG. 2B, the fasteners are not shown for thesake of clarity in illustrating the remaining components.

The seat back fold-down and adjustable seat back angle mechanism 124includes a pivot bracket 200, a stop block 202, a back angle adjustmentrod 204, and a bar-slide coupling 206. The seat back 135 includes theback cane 130 and the back cane adjustment rod 204 and the bar slidecoupling 206.

The pivot bracket 200 (FIG. 2A) is an elongated triangular member havingthree vertices or end portions 140, 142 and 144. Each one of thevertices 140–144 of the pivot bracket 200 has a respective fasteneropening in the form of a through hole.

The stop block 202 (FIGS. 3 and 4) is a solid member having an arcuatebearing surface 306 adapted to fit closely over the rail 114. The stopblock 200 also has a pin channel 302 disposed above the bearing surface306. The pin channel 302 extends in a front to back direction when thestop block 200 is mounted on the frame rail 114.

The stop block 200 further has a cam surface 304 disposed above the pinchannel 302. The stop block 200 also has a planar bearing surface 308that is disposed below the pin channel 302. The bearing surface 308partially defines an adjustment bar channel 309, in the stop block 200,that extends parallel to the pin channel 302.

The back angle adjustment rod 204 is a solid member that has alongitudinally extending slot 234 that extends completely through(radially across) the rod. A stepped bore 310 extends downwardly fromthe slot 234. The bore 310 does not extend completely through (radiallyacross) the rod 204, but instead is only present on one side (theinside) of the rod.

The stepped bore 310 comprises a plurality of interconnecting circularapertures 311 configured to receive a plunger pin. It should beunderstood that the particular geometry of bore 310 is not important solong as it is configured to allow a plunger pin to lock in a selectedone of the apertures 311 of the bore 310. Hence, the bore 310 can beimplemented using, for example, rectangular, square, oval, or triangulargeometries.

The back angle adjustment rod 204 has a lower end portion 156. The lowerend portion 156 of the back angle adjustment rod 204 includes a threadedbore 205 that extends completely through (radially across) the lower endportion. The lower end portion 156 has an arcuate lower end surface orbearing surface 219.

The bar slide coupling 206 has a hollow tubular configuration includinga central passage 158 (FIGS. 2A and 2B) that extends completely throughthe bar slide coupling. The bar slide coupling 206 has a hollow tubularsleeve portion 207 with a radially extending fastener opening 211. Abase portion 203 of the bar slide coupling 206 extends downward from thesleeve portion 207. The base portion 203 has on its outside a fasteneropening in the form of a threaded bore 162. The base portion 203 has onits inside a fastener opening in the form of a threaded bore 166. Thethreaded bore 166 opens into the central passage 158 in the base portion203 of the bar slide coupling 206.

In assembly of the mechanism 124, the sleeve portion 207 of the barslide coupling 206 is inserted into the tubular lower end portion of theback cane 130. The fastener opening 211 in the sleeve portion 207 of thebar slide coupling 206 aligns with a fastener opening 215 in the backcane 130. The base portion 203 of the bar slide coupling 206 extendsoutside of and below the back cane 130.

The back angle adjustment rod 204 (FIGS. 2A and 2B) is slid into thepassage 158 in the bar slide coupling 206. The upper slot 234 in theback angle adjustment rod 204 aligns with the opening 211 in the barslide coupling 206. Portions of the back angle adjustment rod 204,including the stepped bore 310 and the bore 205, project downward out ofthe bar slide coupling 206.

The second or upper end portion 142 of the pivot bracket 200 is thenplaced adjacent to the back cane 130. A bolt 212 is placed through thefastener opening in the upper end portion 142 of the pivot bracket 200and through the opening 215 in the back cane 130. The bolt 212 extendsthrough the fastener opening 211 in the sleeve portion 207 of the barslide coupling 206. The bolt 212 also extends through the upper slot 234in the back angle adjustment rod 204.

A nut 213 is secured on the bolt 212. The upper end portion 142 of thepivot bracket 200, and the back cane 130, are thus permanently connectedto each other by the bolt 212. The bolt 212 also secures the bar slidecoupling 206 permanently in place in the lower end of the back cane 130.

The back angle adjustment rod 204 is supported for sliding movement inthe bar slide coupling 206 and in the back cane 130. The engagement ofthe bolt 212 with the ends of the slot 234 prevents the back angleadjustment rod 204 from coming out the back cane 130.

Separately, the first or forward end portion 140 of the pivot bracket200 is secured to the frame rail 114, at a location forward of the upperend portion 142, by a forward bolt 208 and a nut 209. The pivot bracket200 is thus supported on the rail 114 for pivotal movement relative tothe rail about the forward bolt 208. As a result, the lower end portionof the back cane 130, the bar slide coupling 206 and the back angleadjustment rod 204, which are connected with each other and with theupper end portion 142 of the pivot bracket 200 by the bolt 212, are alsosupported by the pivot bracket for pivotal movement relative to the rail114 about the forward bolt 208.

Separately, the bar slide coupling 206 is secured to the pivot bracket200 by a lower bolt 210. The lower bolt 210 extends through the fasteneropening in the lower end portion 144 of the pivot bracket 200 and isscrewed into the threaded bore 162 in the bar slide coupling 206. As aresult, the pivot bracket 200 and the bar slide coupling 206 arepermanently connected to each other by the lower bolt 210.

The pivot bracket 200 is thus secured to the bar slide coupling 206 bythe lower bolt 208; is secured to the back cane 130 by the upper bolt212; and is pivotally secured to the rail 114 by the forward bolt 208.

The assembly of the back cane 130 and the back cane adjustment rod 204is connected with the pivot bracket 200 at two locations along itslength, i.e., at the upper bolt 212 and the lower bolt 210. As a result,the back cane 130 and the back cane adjustment rod 204 are fixed to thepivot bracket for movement with the pivot bracket relative to the framerail 114. The back cane 130 does not pivot relative to the pivot bracket200.

Also separately, the stop block 202 is fixedly secured to the rail 114by a bolt 214 and a nut 216, at a location rearward of the forward bolt208. The curved bearing surface 306 on the stop block 202 overlies thecurved outer surface of the rail 114. The pin channel 302 and theadjustment channel 309 on the stop block 202 are disposed above the rail114. The flat bearing surface 308 on the stop block faces upwardly. Thecam surface 304 on the stop block 202 also faces upwardly.

A lower plunger pin assembly 217 is mounted on the back angle adjustmentrod 304. The lower plunger pin assembly 217 includes a pull ring 218, anexternally threaded plunger housing 220, a compression spring 222, and aplunger pin 224. The plunger housing 220 is screwed into the threadedbore 205 in the lower end portion 217 of the back angle adjustment bar204. As a result, the lower plunger pin assembly 217 is fixed in andmovable with the back angle adjustment bar 204. The lower plunger pinassembly 217 constitutes a first releasable locking mechanism of theadjustment mechanism 124.

In assembly, the lower end portion 156 of the back angle adjustment bar304, with the lower plunger pin assembly 217 affixed thereon, ispositioned adjacent the stop block 202. The arcuate lower end surface219 of the back angle adjustment bar 304 abuttingly engages the flatbearing surface 308 on the stop block 202 to transmit vertical load fromthe back cane 130 to the stop block 202 and thereby the frame rail 114.

The plunger pin 224 extends through the lower end portion 156 of theback angle adjustment bar 304 and into the pin channel 302 on the stopblock 202. The engagement of the plunger pin 224 in the pin channel 302of the stop block 202 prevents the back cane adjustment rod 204 frommoving upwardly (as viewed in FIGS. 3 and 4) relative to and off thestop block. This prevents the back angle adjustment bar 304 from beingpulled off the rail 114 and thus prevents the back cane 130 and theentire seat back from being folded forward onto the seat bottom cushion.

The wheelchair also includes an upper plunger pin assembly 225. Theupper plunger pin assembly 225 includes a pull ring 226, an externallythreaded plunger housing 228, a compression spring 230, and a plungerpin 232. The plunger housing 220 is screwed into the threaded bore 166in the base portion 203 of the bar slide coupling 206. As a result, theupper plunger pin assembly 225 is fixed in and movable with the barslide coupling 206. The upper plunger pin assembly 225 constitutes asecond releasable locking mechanism of the adjustment mechanism 124.

The plunger pin 232 extends completely through the threaded bore 166 inthe bar slide coupling 206 and radially into the passage 158 in the barslide coupling. Because the back cane adjustment rod 204 extends axiallythrough the passage 158 in the bar slide coupling 206, the plunger 232pin thus extends radially into the stepped lower slot 310 of the backangle adjustment bar.

The plunger 232 pin is received in and engages in one of the apertures311 of the lower slot 310 of the back cane adjustment rod 204. Thisengagement prevents the back cane adjustment rod 204 from movingvertically (axially), relative to and inside of, the bar slide coupling206. Because the bar slide coupling 206 is fixed in position verticallyin the back cane 130 by the bolt 212, the plunger pin 232 thus blocksaxial movement of the back cane adjustment rod 204 in the back cane 130.

The upper plunger pin assembly 225 thus fixes the relative verticalposition of the back cane adjustment rod 204 in the back cane 130.Selecting an opening 311 in the back cane adjustment rod 204 forreceiving the plunger pin 232, as described below, can adjust the angle(tilt) of the seat back relative to the frame rails 114.

If it is desired to fold the seat back assembly forward onto the seatbottom cushion and frame rail 114 (see FIGS. 3–6), the pull ring 218 ofthe lower plunger pin assembly 217 is pulled away from its housing 220.The plunger pin 224 moves horizontally out of the pin channel 302 on thestop block, as is shown in FIG. 5. As a result, the pivot bracket 200 isfreely pivotable relative to the frame rail 114 about the forward bolt208. Thus, the back cane adjustment rod 130 and the back cane 204, whichare connected with the pivot bracket 200 by the bolts 210 and 212, arefree to move relative to the stop block 202 and, therefore, relative tothe frame rail 114 on which the stop block is affixed. The seat backassembly, which remains pivotally connected to the rail 114 by the pivotbracket 200 and the bolt 208, can then be tipped forward, pivotingaround the bolt 208. The parts move to the folded position shown in FIG.6.

To unfold and lock the seat back, the seat back assembly is moved backfrom the position shown in FIG. 6 to the position shown in FIGS. 3 and4. As this movement occurs, the tip of the plunger pin 224 engages thecam surface 304 on the stop block 202. The cam surface 304 cams andretracts the plunger pin 224 into the housing 220 so that the plungerpin can move into a position laterally adjacent to the pin channel 302in the stop block 202.

The plunger pin 224 enters vertically into the pin channel 302 on thestop block 202 and, under the force of the spring 222, is pushed outwardof the housing 220 (horizontally) into engagement with the surfacesdefining the pin channel in the stop block. The engagement of theplunger pin 224 in the pin channel 302 connects the lower plunger pinassembly 217 with the stop block 202. Because the lower plunger pinassembly 217 is secured to the back cane adjustment rod 204, thisengagement also secures the back angle adjustment bar to the stop block202. Because the back cane adjustment rod 204 is secured to the backcane 130, the back cane is thus secured to the stop block 202. The seatback assembly is thus unfolded and secured again to the rail 114 and cannot be folded forward without locking again.

When the seat back assembly is, in this manner, being folded forward orback, the adjustment of the upper plunger pin assembly 225 in thestepped slot 310 is not affected. The plunger pin 232 remains fully inthe selected aperture 311 of the stepped slot 310, without change. Thus,the angle of the seat back relative to the lower rail 114 is notaffected

The plunger pin 232 can selectively be placed in any one of theapertures 311 of the lower slot 310 of the back cane adjustment rod 204.When this occurs, the tilt of the seat back changes, thus changing theangle of the seat back relative to the seat bottom cushion.

Specifically, when the pull ring 226 of the upper plunger pin assembly225 is pulled, the plunger pin 232 is pulled laterally out of thestepped bore 310 in the back angle adjustment bar 130. The assembly ofthe back cane 204 and the bar slide coupling 206 is then free to movevertically relative to the back cane adjustment rod 204, which is heldin position on the frame rail 114 by the lower plunger pin assembly 217.

A downward force may be applied to the back cane 130, for example,through the handle bar 134 (FIG. 1). This force causes the back cane130, the bar slide coupling 206, and the upper plunger pin assembly 225to move downward in a telescopic fashion along the back cane adjustmentrod 204.

Once the desired seat back angle is achieved, the plunger ring 226 isreleased and the plunger pin 232 is allowed to move back, under theforce of the spring 230, into the selected aperture 311 of the steppedbore 310. This engagement locks the parts together and sets the angle ofthe seat back relative to the seat bottom cushion. It should beunderstood that an upward force could also be applied to the back cane130, bar-slide coupling 206, and plunger pin assembly 225, resulting inan angle adjustment in the opposite direction.

As the back cane 130 moves upward and downward along the back caneadjustment rod 204, the length of the seat back 135 varies, and theangle of the seat back including the back cane, relative to the framerail 114, changes. This change occurs because the lower end portion 156of the back cane adjustment rod 204 is blocked from vertical movementrelative to the rail 114 by the engagement of the plunger pin 224 in thepin channel 302 of the stop block 202,

The plunger pin 232 is, however, free to move laterally along thefore-and-aft length of the pin channel 302 in the stop block 202.Therefore, as the angle between the back cane 130 and the frame rail 114is adjusted as described above, the pivot bracket 200 pivots relative toboth the back cane 130 and the frame rail 114, as can be seen in theseries of views shown in FIG. 7–9 showing different positions of suchangular adjustment. The plunger pin 232 moves laterally along the lengthof the channel 302 in the stop block 202, as the lower end portion 156of the back cane adjustment rod 204 slides forward or rearward in thechannel 309 and along the bearing surface 306 of the stop block which isfixed to the rail 114. In addition, the bolt 212 moves vertically in theupper slot 210 in the back cane adjustment rod 204.

This adjustment of the angle of the seat back assembly is effectedwithout detaching the lower plunger pin assembly 217 including theplunger pin 224 from the stop block 202 in the manner described abovewith reference to the fold-down feature of the wheelchair. Conversely,the fold-down feature can be utilized without affecting the particularsetting of the seat back angle, because the plunger pin 232 remains inthe selected aperture 311 in the stepped bore 310.

The bolt 212 extends completely through the upper slot 234 in the backcane adjustment rod 204, as well as through the fastener opening 215 inthe back cane 130. The bolt 212 thus limits the extent of relativetelescoping movement of the back cane adjustment rod 204 and the backcane 130, setting the extremes of such movement. The bolt 212 alsoprevents the back cane adjustment rod 204 from being pulled completelyout of the back cane 130 when the plunger pin 232 is not engaged in anyof the apertures 311 of the slot 310 of the back angle adjustment bar.

A pull cable 138 (FIG. 1) is provided between the respective lowerplunger pin assemblies 217 of the two seat back fold-down mechanisms 124and 136. By pulling on the pull cable 138 and simultaneously applyingeither an upward or downward force to the handlebar 132, a user canmodify or change the seat back angle adjustment of the back canes 130and 134. As such, the seat back angle adjustment function can beperformed in a simple intuitive manner and without the use of tools.

Similarly, a pull cable 140 is provided between the upper plunger pinassemblies 225 of the two seat back fold-down mechanisms 124 and 136. Bypulling on the pull cable 140 and simultaneously applying a forwardforce to the handlebar 132, a user can release the seat back canes 130and 134 from their locked state and fold them down towards frame portion114. As such, the seat back fold-down function can be performed in asimple intuitive manner and without the use of tools.

Hence, the illustrated embodiment of the present invention providesindependent seat back fold-down functionality and seat back angleadjustment functionality. In particular, the seat back can be foldeddown, or raised from a folded down portion, without disturbing the seatback angle adjustment. Such a feature is accomplished by mounting orattaching the seat back angle adjustment mechanism to a pivot bracketthat is incorporated into the seat back fold-down function. As the pivotbracket pivots to accomplish the fold-down function, the seat back angleadjustment mechanism undergoes a corresponding motion without a changein its adjustment setting.

While the present invention has been illustrated by the description ofembodiments thereof, and while the embodiments have been described inconsiderable detail, it is not the intention of the applicant torestrict or in any way limit the scope of the appended claims to suchdetail. Additional advantages and modifications will readily appear tothose skilled in the art. For example, other type of releasable latchescan be employed instead of plunger pins (e.g., nut and bolt fasteners),channel 302 in stop block 202 can have closed ends, and variouscomponents can be made to differing measurements or proportions thanshown herein. Therefore, the invention, in its broader aspects, is notlimited to the specific details, the representative apparatus, andillustrative examples shown and described. Accordingly, departures canbe made from such details without departing from the spirit or scope ofthe applicant's general inventive concept.

1. A wheelchair including: a seat back; a frame rail; a seat backfold-down mechanism supporting said seat back for folding movementrelative to said frame rail between a folded position and an unfoldedand locked position, said seat back fold-down mechanism including afirst releasable locking mechanism for releasably locking said seat backin the unfolded and locked position; and a seat back angle adjustmentmechanism for adjusting the angle of said seat back relative to saidframe rail when said seat back is in the unfolded and locked position,said seat back angle adjustment mechanism including a second releasablelocking mechanism for releasably locking said seat back at any selectedone of a plurality of different angles relative to said frame rail; saidseat back fold-down mechanism enabling folding movement of said seatback between the folded position and the unfolded and locked positionwithout releasing said second releasable locking mechanism when saidseat back is locked in any selected one of the plurality of differentangles relative to said frame rail; said seat back having a portion thatslides along said frame rail as the seat back angle is adjusted.
 2. Awheelchair as set forth in claim 1 wherein the length of said seat backvaries as the seat back angle is adjusted.
 3. A wheelchair as set forthin claim 2 wherein said seat back is pivotally connected with said framerail by a pivot bracket, said seat back being fixedly connected to saidpivot bracket, said pivot bracket pivoting relative to said frame railwhen said seat back is moved from the unfolded position to the foldedposition.
 4. A wheelchair as set forth in claim 1 wherein said firstreleasable locking mechanism includes a first plunger pin assemblyhaving a plunger pin engageable in a track on said frame rail, and saidsecond releasable locking mechanism includes a second plunger pinassembly having a plunger pin that is selectively engageable in any oneof a plurality of spaced apertures on said seat back.
 5. A wheelchair asset forth in claim 1 wherein the frame rail is a generally horizontalframe rail that does not pivot upon folding of the seat back, thewheelchair including a pivot plate that is pivotally joined to the framerail and that supports the seat back for pivoting movement relative tothe frame rail, the seat back portion sliding along the generallyhorizontal frame rail as the seat back angle is adjusted.
 6. Awheelchair as set forth in claim 1 wherein the seat back portion thatslides along the frame rail as the seat back angle is adjusted comprisesa lower portion of the seat back, the seat back lower portion beingsupported on a track of the frame rail for sliding movement in agenerally horizontal direction along the track and thus along the lengthof the frame rail as the seat back angle is adjusted.
 7. A wheelchair asset forth in claim 6 wherein the first releasable locking mechanismincludes a release pin that is supported on the lower portion of theseat back for movement with the seat back, the release pin having aportion that is slidably received in the track.
 8. A wheelchairincluding: a seat back; a frame rail; a seat back fold-down mechanismsupporting said seat back for folding movement relative to said framerail between a folded position and an unfolded and locked position, saidseat back fold-down mechanism including a first releasable lockingmechanism for releasably locking said seat back in the unfolded andlocked position; and a seat back angle adjustment mechanism foradjusting the angle of said seat back relative to said frame rail whensaid seat back is in the unfolded and locked position, said seat backangle adjustment mechanism including a second releasable lockingmechanism for releasably locking said seat back at any selected one of aplurality of different angles relative to said frame rail; said seatback fold-down mechanism enabling folding movement of said seat backbetween the folded position and the unfolded and locked position withoutreleasing said second releasable locking mechanism when said seat backis locked in any selected one of the plurality of different anglesrelative to said frame rail; said seat back having a length that variesas the seat back angle is adjusted.